Binary volume phase masks in photo-thermo-refractive glass

Abstract

Permanent binary phase masks with planar surfaces and high tolerance to laser radiation are recorded in the volume of photo-thermo-refractive glass using the contact copying technique and binary amplitude master masks. Conversion of a Gaussian beam to higher order modes is shown.

Holographically encoded volume phase masks

“…As demonstrated previously, 20 a four-sector binary phase mask can itself be used as an optical mode converter when the probe beam center is properly aligned with respect to the phase steps. Such a binary phase mask though works only for the particular wavelength for which the phase shift is π.…”

“…PTR glass is a multicomponent photosensitive glass with a transparency window from the near UV to the near IR which has the ability to sustain high power beams. [31][32][33] It has been used in a variety of applications, including producing volume phase masks 20 and holograms for pulse stretching/compression 34 as well as coherent and spectral beam combining. [35][36][37] To fabricate the HPM, a four-sector binary phase mask 20 designed for the recording wavelength of 325 nm was placed in one arm of the setup and the half angle of interference was set to 0.786 deg, giving a grating period of 8 μm.…”

“…(9), which is described in Ref. 20; the experimentally achieved conversion efficiencies are listed in Table 1. The fundamental mode LP 01 has been converted to the even and odd LP 11 modes as well as the LP 21 mode with efficiencies up to 70%, indicating that the calculated maximum conversion efficiencies can be reached in the experiments.…”

“…The first method controls the local geometrical path length by generating a contoured surface, 5,[10][11][12][13][14][15] while the second method changes the local refractive index in the bulk of a photosensitive medium such as lithium niobate or photosensitive glass. 19,20 Both methods can be employed to generate phase masks with almost any profile. However, because the phase shift is induced by changing the local optical path length, these phase masks are inherently limited to use at a specific wavelength, which limits the range of potential applications.…”

Simultaneous laser beam combining and mode conversion using multiplexed volume phase elements

“…PTR glass is a photosensitive glass which has been used in a variety of applications, including producing volume phase masks [5] and beam combining [1][2][3]. A foursector mode converting mask (partially converting a Gaussian beam into the TEM 11 mode) designed for the recording wavelength of 325 nm was placed in one arm of the setup shown in Fig.…”